It is certainly true that Obama’s approval ratings have fallen to Bush-2005 levels. It’s also entirely possible they’ll fall further still: The administration’s panicky preparations for January suggest the first month of actual Obamacare coverage may be just as chaotic and unpopular as the onset of Medicare Part D. Yet the Bush comparisons state, or imply, broader forces at work than mere sagging approval ratings. They suggest a presidency that has hit a new inflection point beyond which its credibility is severed and its agenda broken. And that conclusion falls apart because it completely misses how power works in the Obama era.

If you measure the power of Obama’s presidency as the ability to move his agenda through Congress, his presidency has been dead since Republicans took control of the House in January 2011. If you measure it by his ability to use his popularity to force the opposing party to cooperate, it has literally been dead from the outset. In Obama’s first few weeks, with approval ratings in the seventies, he could not persuade a single House Republican to support a fiscal response to the most dire economic emergency in 80 years.

Bush’s power worked very differently. He enjoyed control of Congress for most of his first term and the first two years of his second. What’s more, his opposition party genuinely feared being seen as obstructionist. Substantial minorities of Democrats decided to vote for elements of Bush’s agenda on the calculation that being seen as bipartisan, and winning narrow concessions, made more political sense than opposing Bush. A dozen Democratic senators voted for the Bush tax cuts, and another seven abstained. Democrats supported the porky energy bill, and could have blocked Medicare Part D through a filibuster but decided not to.

Republicans like to blame Hurricane Katrina for fundamentally breaking Bush’s presidency. It’s a handy rationalization both for Bush loyalists, who can blame his failure on a single freak event, and for conservatives, who can avoid implicating conservative ideology. (They also throw in Republican corruption scandals.) McInturff, a Republican pollster, repeats this mythology in his Bush-is-Obama memo, in which he argues, “Hurricane Katrina is rightly remembered as a dividing point in the Bush presidency.”

Here’s a chart of Bush’s approval ratings. See any “dividing point”? I don’t:

Now, Bush’s approval ratings did fall more steeply in 2005 than at other points. What happened in 2005, before Katrina, is that Bush devoted the entire year to using his popularity to sell the public on a plan to privatize Social Security. Americans loathed the idea, but Republicans thought that if Bush spent enough time selling them on it, he could win them over. Instead both the policy and Bush grew less popular.

Of course, Iraq was also spiraling into dysfunction at the time. But Social Security privatization represented a real break point for Democrats in Congress. Faced with a radical challenge to their governing philosophy (and a genuinely awful proposal), they had to decide whether to continue working with Bush in return for marginal concessions or to oppose him en masse. Social Security privatization flipped their political calculus. Then the 2006 midterms handed control of Congress to Democrats. The first two years of Bush’s second term successively cost him a pliant opposition, and then turned that opposition into a majority.

Obama, by contrast, faced an opposition party that began in the place Bush’s opposition party ended. The political insight of the Republican Congress, and Mitch McConnell in particular, was the recognition that Democrats under Bush had the politics backward. Their path to self-preservation – show America they were willing to reach across the aisle – not only failed but backfired. It made the president more popular, made public opinion more favorable to his party, and thus made them more vulnerable. Since most Americans hold the president responsible for what happens, the opposition party has an incentive to withhold support for anything, making the president seem partisan. As McConnell put it, “It was absolutely critical that everybody be together because if the proponents of the bill were able to say it was bipartisan, it tended to convey to the public that this is O.K., they must have figured it out.”

Obama’s agenda since 2011 worked very differently. He hasn’t lost power the way Bush did, because he never had it — at least not after his first two years. The prospect of Republican cooperation on his agenda was always phantasmal. Unlike Bush, he never had any hope of getting GOP support for major reforms, either by horse trading or by public campaigning. In January, I wrote a column outlining what a successful second Obama term might look like. The most promising avenue for his agenda lay in the use of executive power, especially on climate change. Obama did stand a chance of passing immigration reform.

Almost one year later, the prospects appear about the same. Immigration reform is weaker, but not yet dead. And its weakness has nothing to do with Obama’s popularity — its fate rests on the internal calculus of the House leadership weighing the risks of long-term demographic decline against an immediate conservative revolt.

Obama’s prospects for executive action are actually stronger now. The main impediments to an aggressive regulatory agenda were twofold. First, Republicans could stop regulations by blocking nominees for major agencies. Second, they held a functional majority on the D.C. Circuit Court, and stood poised to block Obama’s environmental and financial reforms. Republicans understood full well the importance of that court to Obama’s second term. (McConnell, again, identified the crucial dynamic: Obama’s second-term agenda, he said, “runs straight through the D.C. Circuit.”) That’s why Republicans took the extraordinary step of declaring a full blockade on any nominee for the court’s three vacancies, however ideologically moderate.

And it’s why the Senate Democrats’ decision to abolish the judicial filibuster looms so large. With a stroke, they eliminated the strongest leverage Republicans have to gum up the president’s second term. Obama has managed to seat nominees to the Federal Housing Authority and the Consumer Financial Protection Bureau. And the odds that the court will overturn new regulations have diminished sharply.

Additionally, Obama has neutralized the most aggressive, confrontational Republican tactics in Congress. In my column from last January, I wrote that Republicans could, through sheer nihilistic confrontation, sow destruction: “They can shut down the government, they can block administrators, they can begin impeachment — to create the kind of political and economic chaos that would make any progress vastly more complicated.” Almost as important as changes in the Senate is Obama’s success at defeating those tactics. In a series of confrontations, he turned Republican threats to shut down the government and default on the national debt against the GOP, persuading its leadership that over-the-top confrontation was self-defeating.

The conventional wisdom – propounded by many of the same pundits now equating Obama with Bush – held that Obama’s hardball tactics would backfire. Obama needed to negotiate over the debt ceiling, and didn’t dare change the Senate’s rules*, argued, to take one example, Ron Fournier. To fail to placate conservatives would only enrage them more. This analysis turned out to have it backward. Congress managed to pass a budget for the first time in three years precisely because Obama defeated the GOP’s extortion tactics, forcing Republicans to actually trade policy concessions rather than demand a ransom.

The prospects for Obama’s second term remain constricted. Not many deals beckon in Congress. The Obamacare rollout was surely a political disaster, but the administration has three more years to get the law up and running. By the end of 2005, George W. Bush had seen the promise of his presidency collapse from justifiably lofty heights. At the end of 2013, Obama stands at just about the same place he began his term.

Update: Fournier did not oppose the nuclear option. I was thinking of other centrist pundits. Mea culpa.